Sulfided superactive multimetallic catalytic composite

ABSTRACT

A novel sulfided superactive multimetallic catalytic composite especially useful for converting hydrocarbons comprises a sulfided combination of a catalytically effective amount of a pyrolyzed rhenium carbonyl component with a porous carrier material containing a uniform dispersion of catalytically effective amounts of a platinum group component, which is maintained in the elemental metallic state during the incorporation and pyrolysis of the rhenium carbonyl component. In a highly preferred embodiment, this novel catalytic composite also contains a catalytically effective amount of a halogen component. The platinum group component, pyrolyzed rhenium carbonyl component, sulfur component, and optional halogen component are preferably present in the multimetallic catalytic composite in amounts, calculated on an elemental basis, corresponding to about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 5 wt. % rhenium, 0.001 to about 0.2 wt. % sulfur, and about 0.1 to about 3.5 wt. % halogen. A key feature associated with the preparation of the subject catalytic composite is reaction of a rhenium carbonyl complex with a porous carrier material containing a uniform dispersion of a platinum group component maintained in the elemental state, whereby the interaction of the rhenium moiety with the platinum group moiety is maximized due to the platinophilic (i.e. platinum-seeking) propensities of the carbon monoxide ligands used in the rhenium reagent.

CROSS-REFERENCES TO RELATED DISCLOSURES

This application is a division of my prior, copending application Ser.No. 45,024 filed June 4, 1979, and issued on Jan. 20, 1981 as U.S. Pat.No. 4,246,095 whicn in turn is a continuation-in-part of my priorapplication Ser. No. 833,332 filed Sept. 14, 1977 and issued Aug. 21,1979 as U.S. Pat. No. 4,165,276. All of the teachings of these priorapplications are specifically incorporated herein by reference.

The subject of the present invention is a novel sulfided superactivemultimetallic catalytic composite which has remarkably superioractivity, selectivity and resistance to deactivation when employed in ahydrocarbon conversion process that requires a catalytic agent havingboth a hydrogenation-dehydrogenation function and a carboniumion-forming function. The present invention, more precisely, involves anovel dual-function sulfided superactive multimetallic catalyticcomposite which quite surprisingly enables substantial improvements inhydrocarbon conversion processes that have traditionally used a platinumgroup metal-containing, dual-function catalyst. According to anotheraspect, the present invention comprehends the improved processes thatare produced by the use of the instant sulfided superactiveplatinum-rhenium catalyst system which is characterized by a uniquereaction between a rhenium carbonyl component and a porous carriermaterial containing a uniform dispersion of a platinum group component,which is maintained in the elemental metallic state during theincorporation and pyrolysis of the rhenium carbonyl component, wherebythe interaction between the rhenium moiety and the platinum group moietyis maximized on an atomic level. In a specific aspect, the presentinvention concerns a catalytic reforming process which utilizes thesubject sulfided catalyst to markedly improve activity, selectivity andstability characteristics associated therewith to a degree notheretofore realized for a sulfided platinum-rhenium catalyst system.Specific advantages associated with use of the present sulfidedsuperactive platinum-rhenium catalyst system in a catalytic reformingprocess relative to those observed with the corresponding sulfided priorart sulfided platinum-rhenium catalyst system are: (1) increased abilityto make octane at low severity operating conditions; (2) enhancedcapability to maximize C₅ + reformate and hydrogen production; (3)augmented ability to expand the catalyst life before regenerationbecomes necessary in conventional temperature-limited catalyticreforming units; (4) increased tolerance to conditions which are knownto increase the rate of production of deactivating coke deposits; (5)diminished requirements for amount of catalyst to achieve same resultsas the prior art catalyst systems at no sacrifice in catalyst lifebefore regeneration; and (6) capability of operating at increased chargerates with the same amount of catalyst and at similar conditions as theprior art catalyst systems without any sacrifice in catalyst life beforeregeneration.

Composites having a hydrogenation-dehydrogenation function and acarbonium ion-forming function are widely used today as catalysts inmany industries, such as the petroleum and petrochemical industry, toaccelerate a wide spectrum of hydrocarbon conversion reactions.Generally, the carbonium ion-forming function is thought to beassociated with an acid-acting material of the porous, adsorptive,refractory oxide type which is typically utilized as the support orcarrier for a heavy metal component such as the metals or compounds ofmetals of Groups V through VIII of the Periodic Table to which aregenerally attributed the hydrogenation-dehydrogenation function.

These catalytic composites are used to accelerate a wide variety ofhydrocarbon conversion reactions such as hydrocracking, hydrogenolysis,isomerization, dehydrogenation, hydrogenation, desulfurization,cyclization, polymerization, alkylation, cracking, hydroisomerization,dealkylation, transalkylation, etc. In many cases, the commercialapplications of these catalysts are in processes where more than one ofthe reactions are proceeding simultaneously. An example of this type ofprocess is reforming wherein a hydrocarbon feedstream containingparaffins and naphthenes is subjected to conditions which promotedehydrogenation of naphthenes to aromatics, dehydrocyclization ofparaffins to aromatics, isomerization of paraffins and naphthenes,hydrocracking and hydrogenolysis of naphthenes and paraffins, and thelike reactions, to produce an octane-rich or aromatic-rich productstream. Another example is a hydrocracking process wherein catalysts ofthis type are utilized to effect selective hydrogenation and cracking ofhigh molecular weight unsaturated materials, selective hydrocracking ofhigh molecular weight materials, and other like reactions, to produce agenerally lower boiling, more valuable output stream. Yet anotherexample is a hydroisomerization process wherein a hydrocarbon fractionwhich is relatively rich in straight-chain paraffin compounds iscontacted with a dual-function catalyst to produce an output stream richin isoparaffin compounds.

Regardless of the reaction involved or the particular process involved,it is of critical importance that the dual-function catalyst exhibit notonly the capability to initially perform its specified functions, butalso that it has the capability to perform them satisfactorily forprolonged periods of time. The analytical terms used in the art tomeasure how well a particular catalyst performs its intended functionsin a particular hydrocarbon reaction environment are activity,selectivity, and stability. And for purposes of discussion here, theseterms are conveniently defined for a given charge stock as follows: (1)activity is a measure of the catalyst's ability to convert hydrocarbonreactants into products at a specified severity level where severitylevel means the conditions used--that is, the temperature, pressure,contact time, and presence of diluents such as H₂ ; (2) selectivityrefers to the amount of desired product or products obtained relative tothe amount of reactants charged or converted; (3) stability refers tothe rate of change with time of the activity and selectivityparameters--obviously, the smaller rate implying the more stablecatalyst. In a reforming process, for example, activity commonly refersto the amount of conversion that takes place for a given charge stock ata specified severity level and is typically measured by octane number ofthe C₅ + product stream; selectivity refers to the amount of C₅ + yield,relative to the amount of the charge, that is obtained at the particularactivity or severity level; and stability is typically equated to therate of change with time of activity, as measured by octane number ofC₅ + product and of selectivity as measured by C₅ + yield. Actually thelast statement is not strictly correct because generally a continuousreforming process is run to produce a constant octane C₅ + product withseverity level being continuously adjusted to attain this result; andfurthermore, the severity level is for this process usually varied byadjusting the conversion temperature in the reaction so that, in pointof fact, the rate of change of activity finds response in the rate ofchange of conversion temperatures and changes in this last parameter arecustomarily taken as indicative of activity stability.

As is well known to those skilled in the art, the principal cause ofobserved deactivation or instability of a dual-function catalyst when itis used in a hydrocarbon conversion reaction is associated with the factthat coke forms on the surface of the catalyst during the course of thereaction. More specifically, in these hydrocarbon conversion processesthe conditions utilized typically result in the formation of heavy, highmolecular weight, black, solid or semi-solid, carbonaceous materialwhich is a hydrogen-deficient polymeric substance having properties akinto both polynuclear aromatic and graphite. This material coats thesurface of the catalyst and thus reduces its activity by shielding itsactive sites from the reactants. In other words, the performance of thisdual-function catalyst is sensitive to the presence of carbonaceousdeposits or coke on the surface of the catalyst. Accordingly, the majorproblem facing workers in this area of the art is the development ofmore active and/or selective catalytic composites that are not assensitive to the presence of these carbonaceous materials and/or havethe capability to suppress the rate of the formation of thesecarbonaceous materials on the catalyst. Viewed in terms of performanceparameters, the problem is to develop a dual-function catalyst havingsuperior activity, selectivity, and stability characteristics. Inparticular, for a reforming process the problem is typically expressedin terms of shifting and stabilizing the C₅ + yield-octane relationshipat the lowest possible severity level--C₅ + yield being representativeof selectivity and octane being proportional to activity.

I have now found a dual-function sulfided and attenuated superactivemultimetallic catalytic composite which possesses improved activity,selectivity and stability characteristics relative to similar catalystsof the prior art when it is employed in a process for the conversion ofhydrocarbons of the type which have heretofore utilized dual-function,platinum group metal-containing catalytic composites such as processesfor isomerization, hydroisomerization, dehydrogenation, desulfurization,denitrogenization, hydrogenation, alkylation, dealkylation,disproportionation, polymerization, hydrodealkylation, transalkylation,cyclization, dehydrocyclization, cracking, hydrocracking, halogenation,reforming and the like processes. In particular, I have now establishedthat a sulfided superactive multimetallic catalytic composite,comprising a sulfided combination of a catalytically effective amount ofa pyrolyzed rhenium carbonyl component with a porous carrier materialcontaining catalytically effective amounts of a platinum groupcomponent, can enable the performance of hydrocarbon conversionprocesses utilizing dual-function catalysts to be substantially improvedif the platinum group component is relatively uniformly dispersedthroughout the porous carrier material prior to contact with the rheniumcarbonyl reagent, if the oxidation state of the platinum group metal ismaintained in the elemental metallic state prior to and during contactwith the rhenium carbonyl reagent and if high temperature treatment inthe presence of oxygen and/or water of the resulting reaction product isavoided. A specific example of my discovery involves my finding that asulfided superactive acidic multimetallic catalytic composite,comprising a sulfided combination of a catalytically effective amount ofa pyrolyzed rhenium carbonyl component with a porous carrier materialcontaining a uniform dispersion of catalytically effective amounts of aplatinum group component, which is maintained in the elemental metallicstate during the incorporation and pyrolysis of the rhenium carbonylcomponent and of a halogen component, can be utilized to substantiallyimprove the performance of a hydrocarbon reforming process whichoperates on a low octane gasoline fraction to produce a high octanereformate or aromatic-rich reformate. In the case of a reformingprocess, some of the major advantages associated with the use of thenovel sulfided multimetallic catalytic composite of the presentinvention include: (1) acquisition of the capability to operate in astable manner in a high severity operation; for example, a low ormoderate pressure reforming process designed to produce a C₅ + reformatehaving an octane of at least about 100 F-1 clear; (2) increased averageactivity for octane upgrading reactions relative to the performance ofprior art bimetallic platinum-rhenium catalyst systems as exemplified bythe teachings of Kluksdahl in his U.S. Pat. No. 3,415,737; and (3)increased capability to maximize C₅ + yield and hydrogen productionrelative to these prior art catalyst systems. In sum, the presentinvention involves the remarkable finding that carefully controlledsulfiding of a catalyst formed by the addition of a pyrolyzed rheniumcarbonyl component to a porous carrier material containing a uniformdispersion of a catalytically effective amount of a platinum groupcomponent, which is maintained in the elemental metallic state duringthe incorporation and pyrolysis of the rhenium carbonyl component, canenable the performance characteristics of the resulting sulfidedsuperactive multimetallic catalytic composite to be sharply andmaterially improved relative to those associated with the correspondingsulfided prior art platinum-rhenium catalyst system.

It is, accordingly, an object of the present invention to provide asulfided superactive multimetallic hydrocarbon conversion catalysthaving superior performance characteristics relative to thecorresponding sulfided prior art platinum-rhenium catalyst systems whenutilized in a hydrocarbon conversion process. A second object is toprovide a sulfided superactive multimetallic acidic catalyst havingdual-function hydrocarbon conversion performance characteristics whichare relatively insensitive to the deposition of coke-forming,hydrocarbonaceous materials thereon and to the presence of sulfurcontaminants in the reaction environment. A third object is to providepreferred methods of preparation of this sulfided superactivemultimetallic catalytic composite which methods insure the achievementand maintenance of its unique properties. Another object is to providean improved sulfided platinum-rhenium catalyst system having superioractivity, selectivity and stability characteristics relative to thesulfided platinum-rhenium catalyst systems of the prior art. Anotherobject is to provide a novel acidic sulfided multimetallic hydrocarbonconversion catalyst which utilizes a pyrolyzed rhenium carbonylcomponent to beneficially interact with and selectively promote anacidic catalyst containing a halogen component and a uniform dispersionof a platinum group component maintained in the metallic state duringthe incorporation and pyrolysis of the rhenium carbonyl component.

Without the intention of being limited by the following explanation, Ibelieve my discovery that rhenium carbonyl can, quite unexpectedly, beused under the circumstances described herein to synthesize an entirelynew type of platinum-rhenium catalyst system, is attributable to one ormore unusual and unique routes to greater platinum-rhenium interactionthat are opened or made available by the novel chemistry associated withthe reaction of a rhenium carbonyl reactant with a supported, uniformlydispersed platinum metal. Before considering in detail each of thesepossible routes to greater platinum-rhenium interaction, it is importantto understand that: (1) "platinum" is used herein to mean any one of theplatinum group metals; (2) the unexpected results achieved with mycatalyst systems are measured relative to the conventionalplatinum-rhenium catalyst systems as taught in, for example, theKluksdahl U.S. Pat. No. 3,415,737; (3) the expression "rhenium moiety"is intended to mean the catalytically active form of the rhenium entityderived from the rhenium carbonyl component in the catalyst system; and(4) metallic carbonyls have been suggested generally in the prior artfor use in making catalysts such as in U.S. Pat. Nos. 3,591,649;4,048,110 and 2,798,051, but no one to my knowledge has ever suggestedusing these reagents in the platinum-rhenium catalyst system,particularly where substantially all of the platinum component of thecatalyst is present in a reduced form (i.e. the metal) prior toincorporation of the rhenium carbonyl component. One route to greaterplatinum-rhenium interaction enabled by the present invention comes fromthe theory that the effect of rhenium on a platinum catalyst is verysensitive to the particle size of the rhenium moiety; since in myprocedure the rhenium is put on the catalyst in a form where it iscomplexed with carbon monoxide molecules which are known to have astrong affinity for platinum, it is reasonable to assume that when theplatinum is widely dispersed on the support, one effect of the COligands is to pull the rhenium moiety towards the platinum sites on thecatalyst, thereby achieving a dispersion and particle size of therhenium moiety in the catalyst which closely imitates the correspondingplatinum conditions (i.e. this might be called a piggy-back theory). Thesecond route to greater platinum-rhenium interaction is similar to thefirst and depends on the theory that the effect of rhenium on a platinumcatalyst is at a maximum when the rhenium moiety is attached toindividual platinum sites; the use of platinophilic CO ligands, ascalled for by the present invention, then acts to facilitate adsorptionor chemisorption of the rhenium moiety on the platinum site so that asubstantial portion of the rhenium moiety is deposited or fixed on ornear the platinum site where the platinum acts to anchor the rhenium,thereby making it more resistant to sintering at high temperature. Thethird route to greater platinum-rhenium interaction is based on thetheory that the active state for the rhenium moiety in therhenium-platinum catalyst system is the elemental metallic state andthat the best platinum-rhenium interaction is achieved when theproportion of the rhenium in the metallic state is maximized; using arhenium carbonyl complex to introduce the rhenium into the catalyticcomposite conveniently ensures availability of more rhenium metalbecause all of the rhenium in this reagent is present in the elementalmetallic state. Another route to greater platinum-rhenium interaction isderived from the theory that oxygen at high temperature is detrimentalto both the active form of the rhenium moiety (i.e. the metal) and thedispersion of same on the support (i.e. oxygen at high temperatures issuspected of causing sintering of the rhenium moiety); since thecatalyst of the present invention is not subject to high temperaturetreatment with oxygen after rhenium is incorporated, maximumplatinum-rhenium interaction is obviously preserved. The final theoryfor explaining the greater platinum-rhenium interaction associated withthe instant catalyst is derived from the idea that the active sites forthe platinum-rhenium catalyst are basically platinum metal crystallitesthat have had their surface enriched in rhenium metal; since the conceptof the present invention requires the rhenium to be laid down on thesurface of well-dispersed platinum crystallites via a platinophilicrhenium carbonyl complex, the probability of surface enrichment isgreatly increased for the present procedure relative to that associatedwith the random, independent dispersion of both crystallites that hascharacterized the prior art preparation procedures. It is of course tobe recognized that all of these factors may be involved to some degreein the overall explanation of the impressive results associated with myattenuated superactive catalyst system. A further fact to be kept inmind is that the conventional sulfided platinum-rhenium catalyst systemshave never been noted for an activity improvement (i.e. the consensus ofthe art is that they give the same activity as the all platinum catalystsystem) but their strong suit has always been very impressive stability;in contrast, my sulfided and attenuated superactive platinum-rheniumcatalyst system gives much better average activity than the conventionalsulfided platinum-rhenium catalyst system.

Against this background then, the present invention is in oneembodiment, a novel multimetallic catalytic composite comprising asulfided combination of a catalytically effective amount of a pyrolyzedrhenium carbonyl component with a porous material containing a uniformdispersion of catalytically effective amounts of a platinum groupcomponent which is maintained in the elemental metallic state during theincorporation and pyrolysis of the rhenium carbonyl component.

In another embodiment, the subject catalytic composite comprises asulfided combination of a catalytically effective amount of a pyrolyzedrhenium carbonyl component with a porous carrier material containing acatalytically effective amount of a halogen component and a uniformdispersion of catalytically effective amounts of a platinum groupcomponent which is maintained in the elemental metallic state during theincorporation and pyrolysis of the rhenium carbonyl component.

In yet another embodiment, the present invention involves a sulfidedcombination of a pyrolyzed rhenium carbonyl component with a porouscarrier material containing a halogen component and a uniform dispersionof a platinum group component which is maintained in the elementalmetallic state during the incorporation and pyrolysis of the rheniumcarbonyl component, wherein these components are present in amountssufficient to result in the composite containing, calculated on anelemental basis, about 0.01 to about 2 wt. % platinum group metal, about0.01 to about 5 wt. % rhenium, about 0.1 to about 3.5 wt. % halogen, andabout 0.001 to about 0.2 wt. % sulfur.

In still another embodiment, the present invention comprises any of thecatalytic composites defined in the previous embodiments wherein theporous carrier material contains, prior to the addition of the pyrolyzedrhenium carbonyl component, not only a platinum group component but alsoa catalytically effective amount of a component selected from the groupconsisting of tin, lead, germanium, cobalt, nickel, iron, zinc,tungsten, chromium, molybdenum, bismuth, indium, gallium, cadmium,tantalum, uranium, copper, silver, gold, one or more of the rare earthmetals and mixtures thereof.

In another aspect, the invention is defined as a catalytic compositecomprising the sulfided and pyrolyzed reaction product formed byreacting a catalytically effective amount of a rhenium carbonyl complexwith a porous carrier material containing a uniform dispersion ofcatalytically effective amounts of a platinum group metal maintained inthe elemental metallic state, subjecting the resulting reaction productto pyrolysis conditions selected to decompose the resulting rheniumcarbonyl component and thereafter, contacting the pyrolyzed reactionproduct with a sulfiding agent at sulfiding conditions.

An ancillary embodiment of the present invention involves a method ofpreparing any of the catalytic composites defined in the previousembodiments, the method comprising the steps of: (a) reacting asulfur-containing rhenium carbonyl complex with a porous carriermaterial containing a uniform dispersion of a platinum group componentmaintained in the elemental metallic state; (b) subjecting the resultingreaction product to pyrolysis conditions selected to decompose theresulting rhenium carbonyl component, without oxidizing either theplatinum group or rhenium components, and to thereby liberate asulfiding agent; and (c) contacting the pyrolyzed reaction product ofstep (b) with said sulfiding agent at sulfiding conditions.

A further embodiment involves a process for the conversion of ahydrocarbon which comprises contacting the hydrocarbon and hydrogen withthe sulfided superactive catalytic composite defined in any of theprevious embodiments at hydrocarbon conversion conditions.

A highly preferred embodiment comprehends a process for reforming agasoline fraction which comprises contacting the gasoline fraction andhydrogen with the sulfided superactive multimetallic catalyticcomposites defined in any one of the prior embodiments at reformingconditions selected to produce a high octane reformate.

An especially preferred embodiment is a process for the production ofaromatic hydrocarbons which comprises contacting a hydrocarbon fractionrich in aromatic precursors and hydrogen with an acidic catalyticcomposite comprising a sulfided combination of a catalytically effectiveamount of a pyrolyzed rhenium carbonyl component with a porous carriermaterial containing a catalytically effective amount of a halogencomponent and a uniform dispersion of a catalytically effective amountof a platinum group component maintained in the elemental metallic stateduring the incorporation and pyrolysis of the rhenium carbonylcomponent. This contacting is performed at aromatic productionconditions selected to produce an effluent stream rich in aromatichydrocarbons.

Other objects and embodiments of the present invention relate toadditional details regarding the essential and preferred catalyticingredients, preferred amounts of ingredients, appropriate methods ofcatalyst preparation, operating conditions for use with the novelcatalyst in the various hydrocarbon conversion processes in which it hasutility, and the like particulars, which are hereinafter given in thefollowing detailed discussion of each of the essential and preferredfeatures of the present invention.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the hydrocarbon conversion process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts such as: (1) activated carbon, coke, orcharcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically prepared and naturallyoccurring, which may or may not be acid treated for example, attapulgusclay, china clay, diatomaceous earth, fuller's earth, kaolin,kieselguhr, etc., (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide,cesium oxide, hafnium oxide, zinc oxide, magnesia, boria, thoria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, CaAl₂ O₄, and other like compounds having the formulaMO-Al₂ O₃ where M is a metal having a valence of 2; and (7) combinationsof elements from one or more of these groups. The preferred porouscarrier materials for use in the present invention are refractoryinorganic oxides, with best results obtained with an alumina carriermaterial. Suitable alumina materials are the crystalline aluminas knownas gamma-, eta-, and theta-alumina, with gamma- or eta-alumina givingbest results. In addition, in some embodiments the alumina carriermaterial may contain minor proportions of other well known refractoryinorganic oxides such as silica, zirconia, magnesia, etc.; however, thepreferred support is substantially pure gamma- or eta-alumina. Preferredcarrier materials have an apparent bulk density of about 0.3 to about0.8 g/cc and surface area characteristics (B.E.T.) such that the averagepore diameter is about 20 to 300 Angstroms, the pore volume is about 0.1to about 1 cc/g and the surface area is about 100 to about 500 m² /g. Ingeneral, best results are typically obtained with a gamma-aluminacarrier material which is used in the form of spherical particleshaving: a relatively small diameter (i.e. typically about 1/16 inch), anapparent bulk density of about 0.3 to about 0.8 g/cc, a pore volume(B.E.T.) of about 0.4 to about 0.6 cc/g and a surface area (B.E.T.) ofabout 150 to about 250 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide, to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere, and alumina spheres may becontinuously manufactured by the well known oil drop method withcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resultant hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. This treatment effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

Another particularly preferred alumina carrier material is synthesizedfrom a unique crystalline alumina powder which has been characterized inU.S. Pat. Nos. 3,852,190 and 4,012,313 as a byproduct from a Zieglerhigher alcohol synthesis reaction as described in Ziegler's U.S. Pat.No. 2,892,858. For purposes of simplification, the name "Ziegleralumina" is used herein to identify this material. It is presentlyavailable from the Conoco Chemical Division of Continental Oil Companyunder the trademark Catapal. This material is an extremely high purityalpha-alumina monohydrate (boehmite) which after calcination at a hightemperature has been shown to yield a high purity gammaalumina. It iscommercially available in three forms: (1) Catapal SB--a spray driedpowder having a typical surface area of 250 m² /g; (2) Catapal NG--arotary kiln dried alumina having a typical surface area of 180 m² /g;and (3) Dispal M--a finely divided dispersable product having a typicalsurface area of about 185 m² /g. For purposes of the present invention,the preferred starting material is the spray dried powder, Catapal SB.This alpha-alumina monohydrate powder may be formed into a suitablecatalyst material according to any of the techniques known to thoseskilled in the catalyst carrier material forming art. Spherical carriermaterial particles can be formed, for example, from this Ziegler aluminaby: (1) converting the alpha-alumina monohydrate powder into an aluminasol by reaction with a suitable peptizing agent and water and thereafterdropping a mixture of the resulting sol and a gelling agent into an oilbath to form spherical particles of an alumina gel which are easilyconverted to a gamma-alumina carrier material by known methods; (2)forming an extrudate from the powder by established methods andthereafter rolling the extrudate particles on a spinning disc untilspherical particles are formed which can then be dried and calcined toform the desired particles of spherical carrier material; and (3)wetting the powder with a suitable peptizing agent and thereafterrolling particles of the powder into spherical masses of the desiredsize in much the same way that children have been known to make parts ofsnowmen by rolling snowballs down hills covered with wet snow. Thisalumina powder can also be formed in any other desired shape or type ofcarrier material known to those skilled in the art such as rods, pills,pellets, tablets, granules, extrudates and the like forms by methodswell known to the practitioners of the catalyst carrier material formingart. The preferred type of carrier material for the present invention isa cylindrical extrudate having a diameter of about 1/32" to about 1/8"(especially about 1/16") and a length to diameter (L/D) ratio of about1:1 to about 5:1, with a L/D ratio of about 2:1 being especiallypreferred. The especially preferred extrudate form of the carriermaterial is preferably prepared by mixing the alumina powder with waterand a suitable peptizing agent such as nitric acid, acetic acid,aluminum nitrate and the like material until an extrudable dough isformed. The amount of water added to form the dough is typicallysufficient to give a loss on ignition (LOI) at 500° C. of about 45 to 65wt. %, with a value of about 55 wt. % being especially preferred. On theother hand, the acid addition rate is generally sufficient to provideabout 2 to 7 wt. % of the volatile free alumina powder used in the mix,with a value of about 3 to 4% being especially preferred. The resultingdough is then extruded through a suitably sized die to form extrudateparticles. These particles are then dried at a temperature of about 500°to 800° F. for a period of about 0.1 to about 5 hours and thereaftercalcined at a temperature of about 900° F. to about 1500° F. for aperiod of about 0.5 to about 5 hours to form the preferred extrudateparticles of the Ziegler alumina carrier material. In addition, in someembodiments of the present invention the Ziegler alumina carriermaterial may contain minor proportions of other well known refractoryinorganic oxides such as silica, titanium dioxide, zirconium dioxide,chromium oxide, beryllium oxide, vanadium oxide, cesium oxide, hafniumoxide, zinc oxide, iron oxide, cobalt oxide, magnesia, boria, thoria,and the like materials which can be blended into the extrudable doughprior to the extrusion of same. In the same manner crystalline zeoliticaluminosilicates such as naturally occurring or synthetically preparedmordenite and/or faujasite, either in the hydrogen form or in a formwhich has been treated with a multivalent cation, such as a rare earth,can be incorporated into this carrier material by blending finelydivided particles of same into the extrudable dough prior to extrusionof same. A preferred carrier material of this type is substantially pureZiegler alumina having an apparent bulk density (ABD) of about 0.6 to 1g/cc (especially an ABD of about 0.7 to about 0.85 g/cc), a surface area(B.E.T.) of about 150 to about 280 m² /g (preferably about 185 to about235 m² /g), and a pore volume (B.E.T.) of about 0.3 to about 0.8 cc/g.

A first essential ingredient of the subject catalyst is the platinumgroup component. That is, it is intended to cover the use of platinum,iridium, osmium, ruthenium, rhodium, palladium, or mixtures thereof as afirst component of the attenuated superactive catalytic composite. It isan essential feature of the present invention that substantially all ofthis platinum group component is uniformly dispersed throughout theporous carrier material in the elemental metallic state during theincorporation and pyrolysis of the rhenium carbonyl ingredient.Generally, the amount of this component present in the form of catalyticcomposites is small and typically will comprise about 0.01 to about 2wt. % of final catalytic composite, calculated on an elemental basis.Excellent results are obtained when the catalyst contains about 0.05 toabout 1 wt. % of platinum, iridium, rhodium, palladium or rutheniummetal. Particularly preferred mixtures of these platinum group metalspreferred for use in the composite of the present invention are: (1)platinum and iridium, (2) platinum and rhodium, and (3) platinum andruthenium.

This platinum group component may be incorporated into the porouscarrier material in any suitable manner known to result in a relativelyuniform distribution of this component in the carrier material such ascoprecipitation or cogelation, ion-exchange or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of platinum group metal to impregnate thecarrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic or chloroiridic or chloropalladicacid. Other water-soluble compounds or complexes of platinum groupmetals may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium (II)hydroxide, tetramminepalladium (II) chloride, hexamminerhodium chloride,rhodium carbonylchloride, rhodium trichloride hydrate, rhodium nitrate,sodium hexachlororhodate (III), sodium hexanitrorhodate (III), iridiumtribromide, iridium dichloride, iridium tetrachloride, sodiumhexanitroiridate (III), potassium or sodium chloroiridate, potassiumrhodium oxalate, etc. The utilization of a platinum, iridium, rhodium,or palladium chloride compound, such as chloroplatinic, chloroiridic, orchloropalladic acid or rhodium trichloride hydrate, is preferred sinceit facilitates the incorporation of both the platinum group componentand at least a minor quantity of the preferred halogen component in asingle step. Hydrogen chloride or the like acid is also generally addedto the impregnation solution in order to further facilitate theincorporation of the halogen component and the uniform distribution ofthe metallic components throughout the carrier material. In addition, itis generally preferred to impregnate the carrier material after it hasbeen calcined in order to minimize the risk of washing away the valuableplatinum group compound.

It is especially preferred to incorporate a halogen component into theplatinum group metal-containing porous carrier material prior to thereactions thereof with the rhenium carbonyl reagent. Although theprecise form of the chemistry of the association of the halogencomponent with this carrier material is not entirely known, it iscustomary in the art to refer to the halogen component as being combinedwith the carrier material or with the platinum group component in theform of the halide (e.g. as the chloride). This combined halogen may beeither fluorine, chlorine, iodine, bromine, or mixtures thereof. Ofthese, fluorine and, particularly, chlorine are preferred for thepurposes of the present invention. The halogen may be added to thecarrier material in any suitable manner, either during preparation ofthe support or before or after the addition of the platinum groupcomponent. For example, the halogen may be added, at any stage of thepreparation of the carrier material or to the calcined carrier material,as an aqueous solution of a suitable, decomposable halogen-containingcompound such as hydrogen fluoride, hydrogen chloride, hydrogen bromide,ammonium chloride, etc. The halogen component or a portion thereof, maybe combined with the carrier material during the impregnation of thelatter with the platinum group and/or zinc component, for example,through the utilization of a mixture of chloroplatinic acid and hydrogenchloride. In another situation, the alumina hydrosol which is typicallyutilized to form a preferred alumina carrier material may containhalogen and thus contribute at least a portion of the halogen componentto the final composite. For reforming, the halogen will be typicallycombined with the carrier material in an amount sufficient to result ina final composite that contains about 0.1 to about 3.5%, and preferablyabout 0.5 to about 1.5%, by weight of halogen, calculated on anelemental basis. In isomerization or hydrocracking embodiments, it isgenerally preferred to utilize relatively larger amounts of halogen inthe catalyst--typically, ranging up to about 10 wt. % halogen calculatedon an elemental basis, and more preferably, about 1 to about 5 wt. %. Itis to be understood that the specified level of halogen component in theinstant sulfided superactive catalyst can be achieved or maintainedduring use in the conversion of hydrocarbons by continuously orperiodically adding to the reaction zone a decomposablehalogen-containing compound such as an organic chloride (e.g. ethylenedichloride, carbon tetrachloride, t-butyl chloride) in an amount ofabout 1 to 100 wt. ppm. of the hydrocarbon feed, and preferably about 1to 10 wt. ppm.

After the platinum group is combined with the porous carrier material,the resulting platinum group metal-containing carrier material willgenerally be dried at a temperature of about 200° F. to about 600° F.for a period of typically about 1 to about 24 hours or more andthereafter oxidized at a temperature of about 700° F. to about 1100° F.in an air or oxygen atmosphere for a period of about 0.5 to about 10 ormore hours sufficient to convert substantially all of the platinum groupcomponent to the corresponding platinum group metal oxide. When thepreferred halogen component is utilized in the present composition, bestresults are generally obtained when the halogen content of the platinumgroup metal-containing carrier material is adjusted during at least aportion of this oxidation step by including a halogen or ahalogen-containing compound in the air or oxygen atmosphere utilized.For purposes of the present invention, the particularly preferredhalogen is chlorine and it is highly recommended that the halogencompound utilized in this halogenation step be either hydrochloric acidor a hydrochloric acid-producing substance. In particular, when thehalogen component of the catalyst is chlorine, it is preferred to use amolar ratio of H₂ O to HCl of about 5:1 to about 100:1 during at least aportion of this oxidation step in order to adjust the final chlorinecontent of the catalyst to a range of about 0.1 to about 3.5 wt. %.Preferably, the duration of this halogenation step is about 1 to 5 ormore hours.

A crucial feature of the present invention involves subjecting theresulting oxidized, platinum group metal-and metal-containing, andtypically halogen-treated, carrier material to a substantiallywater-free reduction step before the incorporation of the rheniumcomponent by means of the rhenium carbonyl reagent. The importance ofthis reduction step comes from my observation that when an attempt ismade to prepare the instant catalytic composite without first reducingthe platinum group component, no significant improvement in theplatinum-rhenium catalyst system is obtained. Put another way, it is myfinding that it is essential for the platinum group component to be welldispersed in the porous carrier material in the elemental metallic stateduring the incorporation of the rhenium component by the uniqueprocedure of the present invention in order for synergistic interactionof the rhenium carbonyl component with the dispersed platinum groupmetal to occur according to the theories that I have previouslyexplained. Accordingly, this reduction step is designed to reducesubstantially all of the platinum group component to the elementalmetallic state and to assure a relatively uniform and finely divideddispersion of this metallic component throughout the porous carriermaterial. Preferably a substantially pure and dry hydrogen stream (bythe use of the word "dry" I mean that it contains less than 20 vol. ppm.water and preferably less than 5 vol. ppm. water) is used as thereducing agent in this step. The reducing agent is contacted with theoxidized, platinum group metal-containing carrier material at conditionsincluding a reduction temperature of about 450° F. to about 1200° F., agas hourly space velocity (GHSV) sufficient to rapidly dissipate anylocal concentration of water formed during reduction of the platinumgroup metal oxide, and a period of about 0.5 to about 10 or more hoursselected to reduce substantially all of the platinum group component tothe elemental metallic state. Once this condition of finely divideddispersed platinum group metal in the porous carrier material isachieved, it is important that environments and/or conditions that coulddisturb or change this condition be avoided; specifically, I much preferto maintain the freshly reduced carrier material containing theuniformly dispersed platinum group metal under a blanket of inert gas toavoid any possibility of contamination of same either by water or byoxygen.

A second essential ingredient of the present attenuated superactivecatalytic composite is a rhenium component which I have chosen tocharacterize as a pyrolyzed rhenium carbonyl component in order toemphasize that the rhenium moiety of interest in my invention is therhenium produced by decomposing a rhenium carbonyl complex in thepresence of a finely divided dispersion of a platinum group metal and inthe absence of materials such as oxygen or water which could interferewith the basic desired interaction of the rhenium carbonyl componentwith the platinum group metal component as previously explained. Thisrhenium component may be utilized in the resulting composite in anyamount that is catalytically effective with the preferred amounttypically corresponding to about 0.01 to about 5 wt. % thereof,calculated on an elemental rhenium basis. Best results are ordinarilyobtained with about 0.05 to about 1 wt. % rhenium. The traditional rulefor rhenium-platinum catalyst system is that best results are achievedwhen the amount of the rhenium component is set as a function of theamount of the platinum group component also hold for my composition;specifically, I find that best results with a rhenium to platinum groupmetal atomic ratio of about 0.1:1 to about 10:1, with an especiallyuseful range comprising about 0.2:1 to about 5:1 and with superiorresults achieved at an atomic ratio of rhenium to platinum group metalof about 1:1 to about 3:1.

The rhenium carbonyl ingredient may be reacted with the reduced platinumgroup metal-containing porous carrier material in any suitable mannerknown to those skilled in the catalyst formulation art which results inrelatively good contact between the rhenium carbonyl complex and theplatinum group component contained in the porous carrier material. Oneacceptable procedure for incorporating the rhenium carbonyl compoundinto the composite involves sublimating the rhenium carbonyl complexunder conditions which enable it to pass into the vapor phase withoutbeing decomposed and thereafter contacting the resulting rheniumcarbonyl sublimate with the platinum group metal-containing porouscarrier material under conditions designed to achieve intimate contactof the rhenium carbonyl reagent with the platinum group metal dispersedon the carrier material. Typically this procedure is performed undervacuum at a temperature of about 70° F. to about 250° F. for a period oftime sufficient to react the desired amount of rhenium with the carriermaterial. In some cases, an inert carrier gas such as nitrogen can beadmixed with the rhenium carbonyl sublimate in order to facilitate theintimate contacting of same with the metal-containing porous carriermaterial. A particularly preferred way of accomplishing this rheniumcarbonyl reaction step is an impregnation procedure wherein theplatinum-loaded porous carrier material is impregnated with a suitablesolution containing the desired quantity of the rhenium carbonylcomplex. For purposes of the present invention, organic solutions arepreferred, although any suitable solution may be utilized as long as itdoes not interact with the rhenium carbonyl and cause decomposition ofsame. Obviously the organic solution should be anhydrous in order toavoid detrimental interaction of water with the rhenium carbonylcomplex. Suitable solvents are any of the commonly available organicsolvents such as one of the available ethers, alcohols, ketones,aldehydes, paraffins, naphthenes and aromatic hydrocarbons, for example,acetone, acetyl acetone, benzaldehyde, pentane, hexane, carbontetrachloride, methyl isopropyl ketone, benzene, n-butylether, diethylether, ethylene glycol, methyl isobutyl ketone, diisobutyl ketone andthe like organic solvents. Best results are ordinarily obtained when thesolvent is acetone; consequently, the preferred impregnation solution isa rhenium carbonyl complex dissolved in anhydrous acetone. The rheniumcarbonyl complex suitable for use in the present invention may be eitherthe pure rhenium carbonyl itself or a substituted rhenium carbonyl suchas the rhenium carbonyl halides including the chlorides, bromides, andiodides and the like substituted rhenium carbonyl complexes. Afterimpregnation of the carrier material with the rhenium carbonylcomponent, it is important that the solvent be removed or evaporatedfrom the catalyst prior to decomposition of the rhenium carbonylcomponent by means of the hereinafter described pyrolysis step. Thereason for removal of the solvent is that I believe that the presence oforganic materials such as hydrocarbons or derivatives of hydrocarbonsduring the rhenium carbonyl pyrolysis step is highly detrimental to thesynergistic interaction associated with the present invention. Thissolvent is removed by subjecting the rhenium carbonyl impregnatedcarrier material to a temperature of about 100° F. to about 250° F. inthe presence of an inert gas or under a vacuum condition untilsubstantially no further solvent is observed to come off the impregnatedmaterial. In the preferred case where acetone is used as theimpregnation solvent, this drying of the impregnated carrier materialtypically takes about one half hour at a temperature of about 225° F.under moderate vacuum conditions.

After the rhenium carbonyl component is incorporated into theplatinum-loaded porous carrier material, the resulting composite is,pursuant to the present invention, subjected to pyrolysis conditionsdesigned to decompose substantially all of the rhenium carbonylmaterial, without oxidizing either the platinum group or the decomposedrhenium carbonyl component. This step is preferably conducted in anatmosphere which is substantially inert to the rhenium carbonylcomponent such as in a nitrogen- or noble gas-containing atmosphere.Preferably, this pyrolysis step takes place in the presence of asubstantially pure and dry hydrogen stream. It is of course within thescope of the present invention to conduct the pyrolysis step undervacuum conditions. It is much preferred to conduct this step in thesubstantial absence of free oxygen and substances that could yield freeoxygen under the conditions selected. Likewise, it is clear that bestresults are obtained when this step is performed in the total absence ofwater and of hydrocarbons and other organic materials. I have obtainedbest results in pyrolyzing the rhenium carbonyl component while using ananhydrous hydrogen stream at pyrolysis conditions including atemperature of about 300° F. to about 900° F. or more, preferably about400° F. to about 750° F., a gas hourly space velocity of about 250 toabout 1500 hr.⁻¹ for a period of about 0.5 to about 5 or more hoursuntil no further evolution of carbon monoxide is noted.

An essential feature of the present invention is that the resultingpyrolyzed catalytic composite is subjected to a presulfiding stepdesigned to incorporate sulfur in the form of sulfide into the catalyticcomposite in an amount, calculated on an elemental basis, correspondingto about 0.001 to about 0.2 wt. % sulfur, and especially about 0.005 toabout 0.1 wt. % sulfur. Despite the fact that the precise form of thechemistry of the association of this sulfide component with thecatalytic composite is not entirely known, it is customary in the art torefer to the sulfide component as being physically and/or chemicallycombined with the carrier material and/or with the platinum group andrhenium components in the form of sulfide. This sulfided state can beachieved by contacting the resulting pyrolyzed catalytic composite witha suitable sulfiding agent at appropriate sulfiding conditions selectedto result in a sulfide sulfur content within the ranges previouslyspecified. The sulfiding agent is preferably a suitable decomposablesulfur-containing compound such as hydrogen sulfide, lower molecularweight mercaptans, organic sulfides, etc. Preferably, this procedurecomprises treating the pyrolyzed catalyst with a sulfiding agent such asa mixture of hydrogen sulfide and a diluent gas such as nitrogen orhydrogen at sulfiding conditions sufficient to effect the desiredincorporation of sulfur, generally including a pressure of about 0.1 toabout 10 atmospheres, a temperature ranging from about 50° F. up toabout 1000° F., and a contact time of about 0.1 to 2 or more hours. Itis generally a preferred practice to perform this presulfiding stepunder substantially water-free and oxygen-free conditions. It is withinthe scope of the present invention to maintain or achieve the sulfidedstate of the present catalyst during use in the conversion ofhydrocarbons by continuously or periodically adding a suitable sulfidingagent to the reactor containing the sulfided and attenuated superactivecatalyst in an amount sufficient to provide about 1 to 500 wt. ppm.,preferably about 1 to about 20 wt. ppm. of sulfur, based on hydrocarboncharge. According to an especially preferred mode of operation, thissulfiding step may be accomplished during the pyrolysis step byutilizing a rhenium carbonyl reagent which has a sulfur-containingligand or by adding H₂ S to the hydrogen stream which is preferably usedtherein, during the latter portion of the pyrolysis step.

In embodiments of the present invention wherein the instant sulfidedsuperactive multimetallic catalytic composite is used for thedehydrogenation of dehydrogenatable hydrocarbons or for thehydrogenation of hydrogenatable hydrocarbons, it is ordinarily apreferred practice to include an alkali or alkaline earth metalcomponent in the composite before addition of the rhenium carbonylcomponent and to minimize or eliminate the preferred halogen component.More precisely, this optional ingredient is selected from the groupconsisting of the compounds of the alkali metals--cesium, rubidium,potassium, sodium, and lithium--and the compounds of the alkaline earthmetals--calcium, strontium, barium, and magnesium. Generally, goodresults are obtained in these embodiments when this componentconstitutes about 0.1 to about 5 wt. % of the composite, calculated onan elemental basis. This optional alkali or alkaline earth metalcomponent can be incorporated into the composite in any of the knownways, with impregnation with an aqueous solution of a suitablewater-soluble, decomposable compound being preferred.

An optional ingredient for the sulfided and superactive multimetalliccatalyst of the present invention is a Friedel-Crafts metal halidecomponent. This ingredient is particularly useful in hydrocarbonconversion embodiments of the present invention wherein it is preferredthat the catalyst utilized has a strong acid or cracking functionassociated therewith--for example, an embodiment wherein thehydrocarbons are to be hydrocracked or isomerized with the catalyst ofthe present invention. Suitable metal halides of the Friedel-Crafts typeinclude aluminum chloride, aluminum bromide, ferric chloride, ferricbromide, zinc chloride, and the like compounds, with the aluminumhalides and particularly aluminum chloride ordinarily yielding bestresults. Generally, this optional ingredient can be incorporated intothe composite of the present invention by any of the conventionalmethods for adding metallic halides of this type and either prior to orafter the rhenium carbonyl reagent is added thereto; however, bestresults are ordinarily obtained when the metallic halide is sublimedonto the surface of the carrier material after the rhenium carbonylcomponent is added thereto according to the preferred method disclosedin U.S. Pat. No. 2,999,074. The component can generally be utilized inany amount which is catalytically effective, with a value selected fromthe range of about 1 to about 100 wt. % of the carrier materialgenerally being preferred.

According to the present invention, a hydrocarbon charge stock andhydrogen are contacted with the instant sulfided superactivemultimetallic catalyst in a hydrocarbon conversion zone. This contactingmay be accomplished by using the catalyst in a fixed bed system, amoving bed system, a fluidized bed system, or in a batch type operation;however, in view of the danger of attrition losses of the valuablecatalyst and of well known operational advantages, it is preferred touse either a fixed bed system or a dense-phase moving bed system such asis shown in U.S. Pat. No. 3,725,249. It is also contemplated that thecontacting step can be performed in the presence of a physical mixtureof particles of the catalyst of the present invention and particles of aconventional dual-function catalyst of the prior art. In a fixed bedsystem, a hydrogen-rich gas and the charge stock are preheated by anysuitable heating means to the desired reaction temperature and then arepassed into a conversion zone containing a fixed bed of the sulfided andattenuated superactive multimetallic catalyst. It is, of course,understood that the conversion zone may be one or more separate reactorswith suitable means therebetween to ensure that the desired conversiontemperature is maintained at the entrance of each reactor. It is alsoimportant to note that the reactants may be contacted with the catalystbed in either upward, downward, or radial flow fashion with the latterbeing preferred. In addition, the reactants may be in the liquid phase,a mixed liquid-vapor phase, or a vapor phase when they contact thecatalyst, with best results obtained in the vapor phase.

In the case where the sulfided and superactive multimetallic catalyst ofthe present invention is used in a reforming operation, the reformingsystem will typically comprise a reforming zone containing one or morefixed beds or dense-phase moving beds of the catalysts. In a multiplebed system, it is, of course, within the scope of the present inventionto use the present catalyst in less than all of the beds with aconventional dual-function catalyst being used in the remainder of thebeds. This reforming zone may be one or more separate reactors withsuitable heating means therebetween to compensate for the endothermicnature of the reactions that take place in each catalyst bed. Thehydrocarbon feed stream that is charged to this reforming system willcomprise hydrocarbon fractions containing naphthenes and paraffins thatboil within the gasoline range. The preferred charge stocks are thoseconsisting essentially of naphthenes and paraffins, although in somecases aromatic and/or olefins may also be present. This preferred classincludes straight run gasolines, natural gasoline, synthetic gasolines,partially reformed gasolines, and the like. On the other hand, it isfrequently advantageous to charge thermally or catalytically crackedgasolines or higher boiling fractions thereof. Mixtures of straight runand cracked gasolines can also be used to advantage. The gasoline chargestock may be a full boiling gasoline having an initial boiling point offrom about 50° F. to about 150° F. and an end boiling point within therange of from about 325° F. to about 425° F., or may be a selectedfraction thereof which generally will be a higher boiling fractioncommonly referred to as a heavy naphtha--for example, a naphtha boilingin the range of C₇ to 400° F. In some cases, it is also advantageous tochange pure hydrocarbons or mixtures of hydrocarbons that have beenextracted from hydrocarbon distillates--for example, straight-chainparaffins--which are to be converted to aromatics. It is preferred thatthese charge stocks be treated by conventional catalytic pretreatmentmethods such as hydrorefining, hydrotreating, hydrodesulfurization,etc., to remove substantially all sulfurous, nitrogenous, andwater-yielding contaminants therefrom and to saturate any olefins thatmay be contained therein.

In other hydrocarbon conversion embodiments, the charge stock will be ofthe conventional type customarily used for the particular kind ofhydrocarbon conversion being effected. For example, in a typicalisomerization embodiment, the charge stock can be a paraffinic stockrich in C₄ to C₈ normal paraffins, or a normal butane-rich stock, or ann-hexane-rich stock, or a mixture of xylene isomers, or anolefin-containing stock, etc. In a dehydrogenation embodiment, thecharge stock can be any of the known dehydrogenatable hydrocarbons suchas an aliphatic compound containing 2 to 30 carbon atoms per molecule, aC₄ to C₃₀ normal paraffin, a C₈ to C₁₂ alkylaromatic, a naphthene, andthe like. In hydrocracking embodiments, the charge stock will betypically a gas oil, heavy cracked cycle oil, etc. In addition,alkylaromatics, olefins, and naphthenes can be conveniently isomerizedby using the catalyst of the present invention. Likewise, purehydrocarbons or substantially pure hydrocarbons can be converted to morevaluable products by using the sulfided superactive catalyst of thepresent invention in any of the hydrocarbon conversion processes, knownto the art, that use a dual-function catalyst.

In a reforming embodiment, it is generally preferred to utilize thesulfided superactive multimetallic catalytic composite in asubstantially water-free environment. Essential to the achievement ofthis condition in the reforming zone is the control of the water levelpresent in the charge stock and the hydrogen stream which is beingcharged to the zone. Best results are ordinarily obtained when the totalamount of water entering the conversion zone from any source is held toa level less than 50 ppm. and preferably less than 20 ppm. expressed asweight of equivalent water in the charge stock. In general, this can beaccomplished by careful control of the water present in the charge stockand in the hydrogen stream. The charge stock can be dried by using anysuitable drying means known to the art, such as a conventional solidabsorbent having a high selectivity for water, for instance, sodium orcalcium crystalline aluminosilicates, silica gel, activated alumina,molecular sieves, anhydrous calcium sulfate, high surface area sodium,and the like adsorbents. Similarly, the water content of the chargestock may be adjusted by suitable stripping operations in afractionation column or like device. And in some cases, a combination ofadsorbent drying and distillation drying may be used advantageously toeffect almost complete removal of water from the charge stock. In anespecially preferred mode of operation, the charge stock is dried to alevel corresponding to less than 5 wt. ppm. of water equivalent. Ingeneral, it is preferred to maintain the hydrogen stream entering thehydrocarbon conversion zone at a level of about 10 vol. ppm. of water orless and most preferably about 5 vol. ppm. or less. If the water levelin the hydrogen stream is too high, drying of same can be convenientlyaccomplished by contacting the hydrogen stream with a suitable desiccantsuch as those mentioned above.

In the reforming embodiment, an effluent stream is withdrawn from thereforming zone and passed through a cooling means to a separation zone,typically maintained at about 25° F., wherein a hydrogen-rich gas streamis separated from a high octane liquid product stream, commonly calledan unstabilized reformate. When the water level in the hydrogen streamis outside the range previously specified, at least a portion of thishydrogen-rich gas stream is withdrawn from the separating zone andpassed through an adsorption zone containing an adsorbent selective forwater. The resultant substantially water-free hydrogen stream can thenbe recycled through suitable compressing means back to the reformingzone. The liquid phase from the separating zone is typically withdrawnand commonly treated in a fractionating system in order to adjust thebutane concentration, thereby controlling front-end volatility of theresulting reformate.

The operating conditions utilized in the numerous hydrocarbon conversionembodiments of the present invention are in general those customarilyused in the art for the particular reaction, or combination ofreactions, that is to be effected. For instance, alkylaromatic, olefin,and paraffin isomerization conditions include: a temperature of about32° F. to about 1000° F. and preferably from about 75° F. to about 600°F., a pressure of atmospheric to about 100 atmospheres, a hydrogen tohydrocarbon mole ratio of about 0.5:1 to about 20:1, and a LHSV(calculated on the basis of equivalent liquid volume of the charge stockcontacted with the catalyst per hour divided by the volume of conversionzone containing catalyst and expressed in units of hr.⁻¹) of about 0.2to 10. Dehydrogenation conditions include: a temperature of about 700°F. to about 1250° F., a pressure of about 0.1 to about 10 atmospheres, aliquid hourly space velocity of about 1 to 40, and a hydrogen tohydrocarbon mole ratio of about 1:1 to 20:1. Likewise, typicalhydrocracking conditions include: a pressure of about 500 psig. to about3000 psig., a temperature of about 400° F. to about 900° F., an LHSV ofabout 0.1 to about 10, and hydrogen circulation rates of about 1000 to10,000 SCF per barrel of charge.

In the reforming embodiment of the present invention, the pressureutilized is selected from the range of about 0 psig. to about 1000psig., with the preferred pressure being about 50 psig. to about 600psig. Particularly good results are obtained at low or moderatepressure; namely, a pressure of about 100 to 450 psig. In fact, it is asingular advantage of the present invention that it allows stableoperation at lower pressure than have heretofore been successfullyutilized in so-called "continuous" reforming systems (i.e. reforming forperiods of about 15 to about 200 or more barrels of charge per pound ofcatalyst without regeneration) with conventional sulfidedplatinum-rhenium catalyst systems. In other words, the sulfidedsuperactive multimetallic catalyst of the present invention allowed theoperation of a continuous reforming system to be conducted at lowerpressure (i.e. 100 to about 350 psig.) for about the same or bettercatalyst cycle life before regeneration as has been heretofore realizedwith conventional sulfided platinum-rhenium catalysts at higher pressure(i.e. 300 to 600 psig.).

The temperature required for reforming with the instant catalyst ismarkedly lower than that required for a similar reforming operationusing a high quality sulfided platinum-rhenium catalyst of the priorart. This significant and desirable feature of the present invention isa consequence of the superior activity of the sulfided superactivemultimetallic catalyst of the present invention for the octane-upgradingreactions that are preferably induced in a typical reforming operation.Hence, the present invention requires a temperature in the range of fromabout 775° F. to about 1100° F. and preferably about 850° F. to about1050° F. As is well known to those skilled in the continuous reformingart, the initial selection of the temperature within this broad range ismade primarily as a function of the desired octane of the productreformate considering the characteristics of the charge stock and of thecatalyst. Ordinarily, the temperature then is thereafter slowlyincreased during the run to compensate for the inevitable deactivationthat occurs to provide a constant octane product. Due to the outstandinginitial activity of the catalyst of the present invention, not only isthe initial temperature requirement lower, but also the averagetemperature requirement used to maintain a constant octane product is,for the instant catalyst system, substantially better than for anequivalent operation with a high quality sulfided platinum-rheniumcatalyst system of the prior art; for instance, a sulfided catalystprepared in accordance with the teachings of U.S. Pat. No. 3,415,737.Moreover, it is a singular feature of the catalyst of the presentinvention that the average C₅ + yield and the C₅ + yield stabilityassociated therewith can be markedly superior relative to thoseexhibited by this high quality bimetallic reforming catalyst of theprior art when both catalyst systems are run at equivalent severitylevels. The superior activity, selectivity and stability characteristicsof the instant catalyst can be utilized in a number of highly beneficialways to enable increased performance of a catalytic reforming processralative to that obtained in a similar operation with a sulfidedplatinum-rhenium catalyst of the prior art, some of these are: (1)octane number of C₅ + product can be increased without sacrificingaverage C₅ + yield and/or catalyst run length; (2) the duration of theprocess operation (i.e. catalyst run length or cycle life) beforeregeneration becomes necessary can be increased; (3) C₅ + yield can beincreased by lowering average reactor pressure with no change incatalyst run length; (4) investment costs can be lowered without anysacrifice in cycle life or in C₅ + yield by lowering recycle gasrequirements thereby saving on capital cost for compressor capacity orby lowering initial catalyst loading requirements thereby saving on costof catalyst and on capital cost of the reactors; and (5) throughout canbe increased significantly at no sacrifice in catalyst cycle life or inC₅ + yield if sufficient heater capacity is available.

The reforming embodiment of the present invention also typicallyutilizes sufficient hydrogen to provide an amount of about 1 to about 20moles of hydrogen per mole of hydrocarbon entering the reforming zone,with excellent results being obtained when about 2 to about 6 moles ofhydrogen are used per mole of hydrocarbon. Likewise, the liquid hourlyspace velocity (LHSV) used in reforming is selected from the range ofabout 0.1 to about 10, with a value in the range of about 1 to about 5being preferred. In fact, it is a feature of the present invention thatit allows operations to be conducted at higher LHSV than normally can bestably achieved in a continuous reforming process with a high qualitysulfided platinum-rhenium reforming catalyst of the prior art. This lastfeature is of immense economic significance because it allows acontinuous reforming process to operate at the same throughput levelwith less catalyst inventory or at greatly increased throughput levelwith the same catalyst inventory than that heretofore used withconventional sulfided platinum-rhenium reforming catalyst at nosacrifice in catalyst life before regeneration.

The following examples are given to illustrate further the preparationof the sulfided superactive multimetallic catalytic composite of thepresent invention and the use thereof in the conversion of hydrocarbons.It is understood that the examples are intended to be illustrativerather than restrictive.

EXAMPLE I

A sulfur-free alumina carrier material comprising 1/16 inch spheres wasprepared by: forming an aluminum hydroxy chloride sol by dissolvingsubstantially pure aluminum pellets in a hydrochloric acid solution,adding hexamethylenetetramine to the resulting alumina sol, gelling theresulting solution by dropping it into an oil bath to form sphericalparticles of an alumina-containing hydrogel, aging and washing theresulting particles and finally drying and calcining the aged and washedparticles to form spherical particles of gamma-alumina containing about0.3 wt. % combined chloride. Additional details as to this method ofpreparing the preferred gamma-alumina carrier material are given in theteachings of U.S. Pat. No. 2,620,314.

An aqueous sulfur-free impregnation solution containing chloroplatinicacid and hydrogen chloride was then prepared. The alumina carriermaterial was thereafter admixed with the impregnation solution. Theamount of the metallic reagent contained in this impregnation solutionwas calculated to result in a final composite containing, on anelemental basis, 0.375 wt. % platinum. In order to insure uniformdispersion of the platinum component throughout the carrier material,the amount of hydrogen chloride used in this impregnation solution wasabout 2 wt. % of the alumina particles. This impregnation step wasperformed by adding the carrier material particles to the impregnationmixture with constant agitation. In addition, the volume of the solutionwas approximately the same as the bulk volume of the alumina carriermaterial particles so that all of the particles were immersed in theimpregnation solution. The impregnation mixture was maintained incontact with the carrier material particles for a period of about 1/2 toabout 3 hours at a temperature of about 70° F. Thereafter, thetemperature of the impregnation mixture was raised to about 225° F. andthe excess solution was evaporated in a period of about 1 hour. Theresulting dried impregnated particles were then subjected to anoxidation treatment in a dry air stream at a temperature of about 975°F. and a GHSV of about 500 hr.⁻¹ for about 1/2 hour. This oxidation stepwas desinged to convert substantially all of the platinum ingredient tothe corresponding platinum oxide form. The resulting oxidized sphereswere subsequently contacted in a halogen treating step with an airstream containing H₂ O and HCl in a mole ratio of about 30:1 for about 2hours at 975° F. and a GHSV of about 500 hu.⁻¹ in order to adjust thehalogen content of the catalyst particles to a value of about 1 wt. %.The halogen-treated spheres were thereafter subjected to a secondoxidation step with a dry air stream at 975° F. and a GHSV of 500 hr.⁻¹for an additional period of about 1/2 hour.

The resulting oxidized, halogen-treated, platinum-containing carriermaterial particles were then subjected to a dry reduction treatmentdesigned to reduce substantially all of the platinum component to theelemental state and to maintain a uniform dispersion of this componentin the carrier material. This reduction step was accomplished bycontacting the particles with a hydrocarbon-free, dry hydrogen streamcontaining less than 5 vol. ppm. H₂ O at a temperature of about 1050°F., a pressure slightly above atmospheric, a flow rate of hydrogenthrough the particles corresponding to a GHSV of about 400 hr.⁻¹ and fora period of about one hour.

A sulfur-containing rhenium carbonyl complex, [C₆ H₅ SRe(CO)₃ ]₃, wasthereafter dissolved in an anhydrous acetone solvent in order to preparethe rhenium carbonyl solution which was used as the vehicle for reactingthe rhenium carbonyl complex with the carrier material containing theuniformly dispersed platinum. The amount of this complex used wasselected to result in a finished catalyst containing about 0.375 wt. %rhenium derived from rhenium carbonyl. The resulting rhenium carbonylsolution was then contacted under appropriate impregnation conditionswith the reduced, platinum-containing alumina carrier material particlesresulting from the previously described reduction step. The impregnationconditions utilized were: a contact time of about one half to aboutthree hours, a temperature of about 70° F. and a pressure of aboutatmospheric. It is important to note that this impregnation step wasconducted under a nitrogen blanket so that oxygen was excluded from theenvironment and also this step was performed under anhydrous conditions.Thereafter, the acetone solvent was removed under flowing nitrogen at atemperature of about 175° F. for a period of about one hour. Theresulting dry rhenium carbonyl-impregnated particles were then subjectedto a pyrolysis-sulfiding step designed to decompose the resultingrhenium carbonyl component and simultaneously to liberate a sulfidingagent. This step involved subjecting the rhenium carbonyl-impregnatedparticles to a flowing hydrogen stream at a first temperature of about230° F. for about one half hour at a GHSV of about 600 hr.⁻¹ and atatmospheric pressure. Thereafter, in the second portion of thepyrolysis-sulfiding step the temperature of the impregnated particleswas raised to about 575° F. for an additional interval of about one houruntil the evolution of CO was no longer evident. During the course ofthis step, a sulfiding agent was liberated in situ and thereafterimmediately contacted with the catalyst particles at conditions whichfacilitated the sulfiding of this catalyst system as was manifest by asulfur analysis performed on the resulting catalyst particles whichshowed they picked up about 0.044 wt. % sulfur, calculated on anelemental basis.

A sample of the resulting sulfided and pyrolyzed rhenium-carbonyl andplatinum-containing catalytic composite contained, on an elementalbasis, about 0.375 wt. % platinum, about 0.375 wt. % rhenium derivedfrom the carbonyl, about 1.0 wt. % chlorine, and about 0.044 wt. %sulfur. The resulting catalyst is hereinafter referred to as Catalyst A.For this catalyst, the atomic ratio of rhenium to platinum was about1.05:1 and the atomic ratio of sulfur to platinum was about 0.72:1.

EXAMPLE II

In order to compare the sulfided superactive acidic multimetalliccatalytic composite of the present invention with theplatinum-rhenium-carbonyl catalyst system disclosed in my priorapplication Ser. No. 833,332 in a manner calculated to bring out thebeneficial effects of sulfiding this catalyst system, a comparison testwas made between the catalyst of the present invention prepared inaccordance with Example I, Catalyst A, and a control catalyst, which itis to be emphasized is not a prior art catalyst system but is rather myprior invention as fully disclosed in my prior application Ser. No.833,332 now U.S. Pat. No. 4,165,276. The control catalyst is hereinaftercalled Catalyst B and was manufactured according to the procedure givenin Example I except that the sulfiding step was omitted. This controlcatalyst contained these metals in the same amounts as the catalyst ofthe present invention; that is, the catalyst contained, on an elementalbasis, about 0.375 wt. % platinum, about 0.375 wt. % rhenium, derivedfrom rhenium carbonyl, and about 1.0 wt. % chlorine.

These catalysts were then separately subjected to a high stressaccelerated catalytic reforming evaluation test designed to determine ina relatively short period of time their relative activity, selectivity,and stability characteristics in a process for reforming a relativelylow-octane gasoline fraction. In all tests the same charge stock wasutilized and its pertinent characteristics are set forth in Table I.

This accelerated reforming test was specifically designed to determinein a very short period of time whether the catalyst being evaluated hassuperior characteristics for use in a high severity reforming operation.

                  TABLE I                                                         ______________________________________                                        Analysis of Charge Stock                                                      ______________________________________                                        Gravity, API at 60° F.                                                                         59.1                                                  Distillation Profile, °F.                                              Initial Boiling Point   210                                                   5% Boiling Point        220                                                   10% Boiling Point       230                                                   30% Boiling Point       244                                                   50% Boiling Point       278                                                   70% Boiling Point       292                                                   90% Boiling Point       316                                                   95% Boiling Point       324                                                   End Boiling Point       356                                                   Chloride, wt. ppm.      0.2                                                   Nitrogen, wt. ppm.      0.1                                                   Sulfur, wt. ppm.        0.1                                                   Water, wt. ppm.         10                                                    Octane Number, F-1 clear                                                                              35.6                                                  Paraffins, vol. %       67.4                                                  Naphthenes, vol. %      23.1                                                  Aromatics, vol. %       9.5                                                   ______________________________________                                    

Each run consisted of a series of evaluation periods of 24 hours, eachof these periods comprises a 12-hour line-out period followed by a12-hour test period during which the C₅ + product reformate from theplant was collected and analyzed. The test runs for the Catalysts A andB were performed at identical conditions which comprises a LHSV of 2.0hr.⁻¹, a pressure of 300 psig., a 3.5:1 gas to oil ratio, and an inletreactor temperature which was continuously adjusted throughout the testin order to achieve and maintain a C₅ + target research octane of 100.

Both test runs were performed in a pilot plant scale reforming unitcomprising a reactor containing a fixed bed of the catalyst undergoingevaluation, a hydrogen separation zone, a debutanizer column, andsuitable heating means, pumping means, condensing means, compressingmeans, and the like conventional equipment. The flow scheme utilized inthis plant involves commingling a hydrogen recycle stream with thecharge stock and heating the resulting mixture to the desired conversiontemperature. The heated mixture is then passed downflow into a reactorcontaining the catalyst undergoing evaluation as a stationary bed. Aneffluent stream is then withdrawn from the bottom of the reactor, cooledto about 55° F. and passed to a gas-liquid separation zone wherein ahydrogen-rich gaseous phase separates from a liquid hydrocarbon phase. Aportion of the gaseous phase is then continuously passed through a highsurface area sodium scrubber and the resulting substantially water-freeand sulfur-free hydrogen-containing gas stream is returned to thereactor in order to supply the hydrogen recycle stream. The excessgaseous phase from the separation zone is recovered as thehydrogen-containing product stream (commonly called "excess recyclegas"). The liquid phase from the separation zone is withdrawn therefromand passed to a debutanizer column wherein light ends (i.e. C₁ to C₄)are taken overhead as debutanizer gas and C₅ + reformate streamrecovered as the principal bottom product.

The results of the separate tests performed on the sulfided superactivecatalyst of the present invention, Catalysts A, and the controlcatalyst, Catalyst B, are presented in FIGS. 1, 2 and 3 as a function oftime as measured in days on oil. FIG. 1 shows graphically therelationship between C₅ + yields expressed as liquid volume percent(LV%) of the charge for each of the catalysts. FIG. 2 on the other handplots the observed hydrogen purity in mole percent of the recycle gasstream for each of the catalysts. And finally, FIG. 3 tracks inletreactor temperature necessary for each catalyst to achieve a targetresearch octane number 100.

Referring now to the results of the comparison test presented in FIGS.1, 2 and 3 for Catalysts A and B, it is immediately evident that thesulfided superactive multimetallic catalytic composite of the presentinvention substantially outperformed the platinum-rhenium controlcatalyst in the areas of average hydrogen production and average C₅ +yield. Turning to FIG. 1, it can be ascertained that the average C₅ +selectivity for Catalyst A was clearly superior to that exhibited forCatalyst B with equivalent yield stability. The difference in C₅ + yieldaveraged about 3 vol. % and it is clear evidence that Catalyst A hasmuch better yield octane characteristics than Catalyst B. Hydrogenselectivities for these two catalysts are given in FIG. 2 and it isclear from the data that there is a significant increase in hydrogenselectivity that accompanies the advance of the present invention; Iattribute this increased hydrogen selectivity to the moderating effectof sulfur on the increased metal activity enabled by my uniqueplatinum-rhenium catalyst system. The data presented in FIG. 3immediately highlights the surprising and significant difference inactivity between the two catalyst systems. From the data presented inFIG. 3, it is clear that Catalyst B was consistently about 40° to 45° F.more active than Catalyst A when the two catalysts were run at exactlythe same conditions. The judicious use of the proper amount of a sulfidecomponent in the case of my catalyst system, consequently, provides aconvenient means to trade-off activity for superior C₅ + yield andhydrogen production and allows any superactivated platinum-rheniumcatalyst system to be precisely moderated in order to adjust thesurprising characteristics of this unique catalyst system toapplications where superior C₅ + yield and hydrogen selectivity are moreimportant than extremely high activity.

In final analysis, it is clear from the data presented in FIGS. 1, 2 and3 for Catalysts A and B that the use of a sulfide component to interactwith a platinum-rhenium catalyst system of the type shown in my priorapplication Ser. No. 833,332 now U.S. Pat. No. 4,165,276 provides anefficient and effective means for significantly promoting the C₅ + andhydrogen selectivities of this catalyst system when it is utilized in ahigh severity reforming operation.

It is intended to cover by the following claims all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in the hydrocarbonconversion art or in the catalyst formulation art.

I claim as my invention:
 1. A catalytic composite comprising a sulfidedcombination of both (1) a catalytically effective amount of a pyrolyzedrhenium carbonyl component with a porous carrier material and (2) auniform dispersion of catalytically effective amounts of a platinumgroup component which is maintained in the elemental metallic stateduring the incorporation and pyrolysis of the rhenium carbonylcomponent.
 2. A catalytic composite as defined in claim 1 wherein theplatinum group component is platinum.
 3. A catalytic composite asdefined in claim 1 wherein the platinum group component is ruthenium. 4.A catalytic composite as defined in claim 1 wherein the platinum groupcomponent is rhodium.
 5. A catalytic composite as defined in claim 1wherein the platinum group component is iridium.
 6. A catalyticcomposite as defined in claim 1 wherein the porous carrier materialcontains a catalytically effective amount of a halogen component.
 7. Acatalytic composite as defined in claim 6 wherein the halogen componentis combined chlorine.
 8. A catalytic composite as defined in claim 1wherein the porous carrier material is a refractory inorganic oxide. 9.A catalytic composite as defined in claim 8 wherein the refractoryinorganic oxide is alumina.
 10. A catalytic composite as defined inclaim 1 wherein the composite contains the components in an amount,calculated on an elemental metallic basis, corresponding to about 0.01to about 2 wt. % platinum group metal, about 0.01 to about 5 wt. %rhenium and about 0.001 to about 0.2 wt. % sulfur.
 11. A catalyticcomposite as defined in claim 6 wherein the halogen component is presenttherein in an amount sufficient to result in the composite containing,on an elemental basis, about 0.1 to about 3.5 wt. % halogen.
 12. Acatalytic composite as defined in claim 6 wherein the compositecontains, on an elemental basis, about 0.05 to about 1 wt. % platinumgroup metal, about 0.05 to about 1 wt. % rhenium, about 0.5 to about 1.5wt. % halogen and about 0.005 to about 0.1 wt. % sulfur.
 13. A catalyticcomposite as defined in claim 1 wherein the composite is prepared by thesteps of: (a) reacting a sulfur-containing rhenium carbonyl complex witha porous carrier material containing a uniform dispersion of a platinumgroup component maintained in the elemental metallic state; (b)subjecting the resulting reaction product to pyrolysis conditionsselected to decompose the resulting rhenium carbonyl component and tothereby liberate a sulfiding agent, and (c) contacting the pyrolyzedproduct of step (b) with said sulfiding agent at sulfiding conditions.14. A catalytic composite as defined in claim 13 wherein the pyrolysisstep is conducted under anhydrous conditions and in the substantialabsence of free oxygen.
 15. A catalytic composite comprising thesulfided and pyrolyzed reaction product formed by reacting acatalytically effective amount of a rhenium carbonyl complex with aporous carrier material containing a uniform dispersion of acatalytically effective amount of a platinum group metal maintained inthe elemental metallic state during the incorporation of the rheniumcarbonyl component, subjecting the resulting reaction product topyrolysis conditions selected to decompose the resulting rheniumcarbonyl component, and thereafter, contacting the pyrolyzed reactionproduct with a sulfiding agent at sulfiding conditions wherein saidresultant sulfided composite contains both platinum and rhenium.
 16. Acatalytic composite as defined in claim 15 wherein the porous carriermaterial contains a catalytically effective amount of a halogencomponent.
 17. A catalytic composite as defined in claim 16 wherein thehalogen component is combined chlorine.